The need for high-efficient, high-output, and high-rotation-speed rotary electric machines for industrial applications has been increasing tremendously in response to the need to save energy in light of depleting resources, shortening of machining takt times, or machining of materials that are difficult to machine.
Rotary electric machines are classified into two driving systems: “synchronous” systems and “inductive” systems. Inductive rotary electric machines are often used as rotary electric machines for industrial applications due to their rigidity and strength. However, with inductive rotary electric machines, in principle, current also flows through the rotors. This current generates heat in the rotors, which is a problem in terms of increasing the efficiency and the output of the rotary electric machines. Thus, the use of synchronous rotary electric machines for rotary electric machines for industrial applications is now progressing.
Synchronous rotary electric machines use permanent magnets for generating electric fields in rotors; therefore, in principle, heat is not generated in the rotors, which is advantageous in terms of increasing the efficiency and the output of the rotary electric machines. However, to actually increase the rotational speed of synchronous rotary electric machines, it is necessary to address the problem of separation of the magnets due to the centrifugal force generated during rotation.
A rotary electric machine disclosed in Patent Literature 1 has a structure that prevents such a magnet separation. Specifically, in the rotary electric machine, a plurality of permanent magnets are disposed on the outer peripheral surface of a tubular sleeve member that is fixed to the shaft and the permanent magnets are covered with a protective cover made of carbon fiber reinforced plastics or the like. The inner peripheral surface of the sleeve member is tapered such that its inner diameter increases continuously from one axial end portion toward the other axial end portion.